+<p>You'll also notice that you can specify two port numbers for SMTP: one
+for MTA (Mail Transport Agent) and one for MSA (Mail Submission Agent). The
+traditional ports to use for these purposes are 25 and 587. If you are
+running an external MTA, such as Postfix (which submits mail to Citadel using
+LMTP) or Sendmail (which submits mail to Citadel using the 'citmail'
+delivery agent), that external MTA will be running on port 25, and you should
+specify "-1" for the Citadel MTA port to disable it. The MSA port (again,
+usually 587) would be the port used by end-user mail client programs such as
+Aethera, Thunderbird, Eudora, or Outlook, to submit mail into the system.
+All connections to the MSA port <b>must</b> use Authenticated SMTP.</p>